1. Field of the Invention
The invention relates to a fuel cell vehicle, and more particularly to a fuel cell vehicle provided with an exhaust pipe that releases exhaust gas from a fuel cell system to the outside.
2. Description of the Related Art
Fuel cells have been installed in vehicles because fuel cells produce little effect on environment. In a fuel cell, for example, a fuel gas such as hydrogen is supplied to an anode side of a fuel cell stack, a gas including oxygen, for example air, is supplied as an oxidizing gas to a cathode side of the fuel cell stack, and the electric power is generated by a reaction via an electrolyte membrane as required.
As described above, a reaction of fuel gas and oxidizing gas proceeds in the fuel cell. Therefore, the spent fuel gas and spent oxidizing gas in the reaction are released via an exhaust pipe to the outside as an exhaust gas together with water as a reaction product. In a vehicle, the exhaust pipe is configured to have rearward opening below the vehicle body similarly to the exhaust pipe of a conventional gasoline engine.
Accordingly, where the vehicle travels under the rain or snow, or through deep snow or water pools, water can flood the exhaust pipe, thereby preventing the release of the exhaust gas to the outside. In some cases, water penetrating from the outside can flow back together with the exhaust gas inside the exhaust pipe to the fuel cell. Therefore, backflow in the exhaust pipe has to be prevented.
For example, Japanese Patent Application Publication No. 2008-103276 (JP-A-2008-103276) describes a configuration including an exhaust pipe having a first exhaust channel in which a spent fuel gas released from the fuel cell and a cathode off-gas after the power generation reaction flow separately from each other and a second exhaust channel that is connected to the first exhaust channel and has an exhaust port in the direction perpendicular to the exhaust channel. This configuration does not relate to the penetration of water from the outside, but serves to prevent the backflow in the exhaust pipe. In this configuration, a baffle plate member is provided inside the exhaust pipe to prevent wind from directly entering the inside of the exhaust pipe from the exhaust port.
Japanese Patent Application Publication No. 2008-112679 (JP-A-2008-112679) discloses a configuration in which water vapors contained in a cathode off-gas released from a fuel cell are cooled while flowing in an exhaust pipe of a fuel cell vehicle and partially condensed, but the when the vehicle travels at a constant speed or accelerated, the condensed water is caused to flow from the front to the rear side of the vehicle in the exhaust pipe by the flow of the exhaust gas and an inertia force.
However, it is indicated that where the vehicle is decelerated, the condensed water flows backward and enter the inside of the fuel cell from the exhaust port of the fuel cell. Accordingly, in the JP-A-2008-112679, a step structure is described that includes a first pipe section that is closed at one end, opened as an exhaust port at the other end, and provided with an opening at a predetermined distance from the closed end, and a second pipe section that is connected at one end to the opening and connected at the other end to the fuel cell stack. Further, it is mentioned that because condensed water is stopped by the closed end of the first pipe section, the backflow is prevented.
By providing the baffle plate as described in JP-A-2008-103276, it is possible to prevent to a certain degree the backflow of gas from the outside, and by providing the step structure as in JP-A-2008-112679, it is possible to prevent to a certain degree the backflow of condensed water located inside the exhaust pipe. However, because a fuel cell system generates water as a reaction product, as described hereinabove, the exhaust pipe also has a function of draining water that is the reaction product. In such a case, providing the exhaust pipe with the structures such as described in JP-A-2008-103276 and JP-A-2008-112679 will degrade the draining performance.